Defect properties of vanadium doped barium titanate ceramics

Abstract

X-ray diffraction (XRD) patterns, electron probe microanalysis (EPMA), electron paramagnetic resonance (EPR) powder spectra (9 and 34 GHz) and the magnetic susceptibility of BaTiO _3 + 0.04 BaO + 0.01 V _2 O _5 ceramics were studied to investigate the valence states of V ions and their solubility in the BaTiO _3 lattice. In samples sintered at 1400 °C in air, only about 0.1 mol% V is incorporated in the BaTiO _3 lattice being in V ^4+ and V ^5+ valence state, respectively. 95% of the nominal V dopant content occurs in the secondary phase Ba _3 (V/Ti) _2 O _8 . All BaTiO _3 samples investigated are in tetragonal phase at room temperature. In the as-sintered samples V ^4+ is detected at temperatures T 25 K and vanishing at T > 250 K, which is caused by V ^2+ ions. This spectrum is characterized by a simultaneous HFS and fine structure splitting constituted by allowed and forbidden transitions. Both V ^4+ and V ^2+ ions are incorporated at Ti ^4+ sites of the BaTiO _3 lattice.

Keywords

• barium titanate
• vanadium doped
• defect chemistry
• EPR
• magnetic susceptibility